Women who need a liver transplant are more likely to spend more time on a waiting list, become too sick for transplant or die compared to men. To improve equity, a recently published Vanderbilt-led study suggests a sex adjustment to criteria for MELD (model for end-stage liver disease), which determines allocation of transplanted livers.
The paper, “Proposing a Sex-Adjusted Sodium-Adjusted MELD Score for Liver Transplant Allocation” appears in JAMA Surgery.
To better determine at what point the sex disparity first appears, researchers probed the four lab measurements that the United Network for Organ Sharing (UNOS) uses to determine a transplant candidate’s priority on the waiting list for a donor liver — creatinine, international normalized ratio of prothrombin rate (INR), bilirubin and sodium. Looking at VUMC electronic medical records dating to 1990, researchers studied 623,931 patients.
“Instead of just looking at people who are already on the transplant list, or even people who already have liver disease, we went all the way back to people who are healthy without any liver disease, and we asked, at what point do we start to see these differences between males and females in these labs?” said Lea Davis, PhD, associate professor of Biomedical Informatics, an author of the study. “What we found was that even from the very beginning, prior to any liver disease, females on average have lower values on these labs than males do, and so when they start using these labs to determine the position on the waitlist, it’s as if males have a head start in relation to females.”
To address the disparity, researchers conducted a “translation map” between the MELD scores for males and females that were matched on the degree of illness that patients had, Davis said. Researchers then tested a simulation, applying a proposed sex-adjusted MELD score to liver transplant waiting list data. In the simulated results, the transplant rate in females increased slightly, and overall death decreased. Male waitlist deaths remained unchanged.
“Running that simulation was powerful for us because it was a strong reminder that even a small change that would be easy to implement clinically and may proportionately only change by 1%, for example, could still result in hundreds of lives saved, and that is powerful,” Davis said. “I think it’s both humbling and exciting to be a part of a research team that’s focused on something that’s so immediately beneficial to those who are waiting for liver transplants.”
Other Vanderbilt authors of the study were Julia M. Sealock, PhD, Ioannis A. Ziogas, MD, Zhiguo Zhao, MS, Fei Ye, PhD, Sophoclis Alexopoulos, MD, and Lea Matsuoka, MD.
For future research, Davis suggests comparing the Vanderbilt paper’s method for correcting the sex disparity to other recent scientific proposals to find the best approach. She acknowledges that the sex disparity is the result of multiple factors, and other disparities also exist, including social supports and race.
